1. Field of the Invention
The present invention relates to the augmentation of the thrust provided by a gas generator or other source of a pressurized fluid stream. More specifically, this invention is directed to a thrust augmentor characterized by the combination of a controlled expansion thrust vector control nozzle and an eductor or lift surface wherein secondary flow entrainment efficiency is enhanced by switching flow in the nozzle at a high rate. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
Thrust augmentors are well known in the art. The prior art thrust augmentation devices include those which employ steady-state primary flow out of a nozzle through a large shroud or eductor, or over a Coanda surface, to entrain secondary flow by shearing action. Also known in the prior art are trust augmentors wherein steady-state primary flow out of a series of alternately offset "hypermixing" nozzles is employed to increase entrainment and mixing action; the nozzles discharging into a mixing duct. Further prior art efforts at thrust augmentation include pulse reactors which combine pulse jets with eductors and crypto-steady flow eductors which employ rotating jets discharging into a mixing duct. For a complete description of the crypto-steady flow eductor technology, reference may be had to USAAVLABS Techinical Report 66-18 entitled "Steady-State Thrust Augmentors And Jet Pumps". For a discussion of pulsed reactor type thrust augmentors, reference may be had to Report No. ARD-286 entitled "Interim Summary Report on Investigation Of The Process Of Energy Transform From An Intermittent Jet To Secondary Fluid In An Ejector-Type Thrust Augmentor" submitted to the Office of Naval Research on Mar. 31, 1961 by Hiller Aircraft Corporation. For a discussion of steady-state primary flow eductors and inductors employing "hypermixing" nozzles, reference may be had to an article appearing in J. Aircraft, Volume 9, No. 3, Mar. 1972, at Pages 243-248, by Richard B. Fancher and entitled "Low-Area Ratio, Thrust-Augmenting Ejectors".
Previous thrust augmentors have been characterized by relatively low pumping efficiency and/or complexity and thus lack of reliability. Also, prior art thrust augmentors have usually been of unacceptably large size; it having previously been necessary to employ eductors of large dimension with a long mixing section to approach the desired pumping efficiency. As a consequence of these deficiencies of the prior art, and particularly the low efficiency, prior art thrust augmentation schemes have not been practical for use in the generation of primary lift for VTOL vehicles nor until recently have the previously available devices been sufficiently efficient to enable utilization as VTOL attitude control devices. The inefficiency of prior art thrust augmentors is particularly apparent in off-design operating regimes. It is also noteworthy that prior art thrust augmentation devices and techniques have been further characterized by a lack of flexibility in that usually only a single control variable could be manipulated in an attempt to broaden the operating regime or control pumping efficiency.